Hydroxy-group effect on the regioselectivity in a photochemical oxetane formation reaction (the Paterno-Buechi Reaction) of geraniol derivatives

Article abstract of DOI:10.1039/c1pp05056g

The Paterno-Buechi (PB) reaction of geraniol derivatives 1, which contain allylic alcohol functionality and unfunctionalized double bonds, with benzophenone was investigated to see the effect of the hydroxyl group on the regioselectivity of the oxetane formation, i.e., 2/3. At low concentration of geraniol (1a), oxetanes 2a and 3a were formed in a ratio of 2a/3a = ca. 50/50. The oxetane 2a is derived from the PB reaction at the allylic alcohol moiety, whereas the PB reaction at the unfunctionalized double bond produces the oxetane 3a. The PB reaction of the hydroxy-protected methyl ether 1b and acetate 1c gave selectively oxetanes 3b,c derived from the reaction at the more nucleophilic double bond, 2/3 ～ 15/85. The hydroxyl-group effect was found to be small, but apparently increased the formation of 2a in the PB reaction with geraniol (1a). The Royal Society of Chemistry and Owner Societies.

Full text of DOI:10.1039/c1pp05056g

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PAPER
Hydroxy-group effect on the regioselectivity in a photochemical oxetane
` ¨
formation reaction (the Paterno-Buchi Reaction) of geraniol derivatives†‡
Ken Hisamoto,a Yoshikazu Hiragaa and Manabu Abe*a,b
Received 1st February 2011, Accepted 31st March 2011
DOI: 10.1039/c1pp05056g
The Paterno`–Bu¨chi (PB) reaction of geraniol derivatives 1, which contain allylic alcohol functionality
and unfunctionalized double bonds, with benzophenone was investigated to see the effect of the
hydroxyl group on the regioselectivity of the oxetane formation, i.e., 2/3. At low concentration of
geraniol (1a), oxetanes 2a and 3a were formed in a ratio of 2a/3a = ca. 50/50. The oxetane 2a is derived
from the PB reaction at the allylic alcohol moiety, whereas the PB reaction at the unfunctionalized
double bond produces the oxetane 3a. The PB reaction of the hydroxy-protected methyl ether 1b and
acetate 1c gave selectively oxetanes 3b,c derived from the reaction at the more nucleophilic double bond,
2/3 ~ 15/85. The hydroxyl-group effect was found to be small, but apparently increased the formation
of 2a in the PB reaction with geraniol (1a).
Introduction
Oxetanes, four-membered heterocycles, are key structural units not
only in biologically1 and synthetically2 important compounds, but
also in industrial curing agents.3 Thus, the regio- and stereoselec-
tive preparation of oxetanes is an active area in organic synthesis.
The photochemical [2 + 2] cycloaddition of carbonyls with alkenes,
so-called Paterno`–Bu¨chi (PB) reaction,4 is a useful method for
synthesizing the strained structure. Since the reaction involves
the carbonyl in the electronically excited state, which possesses
a high energy (~70 kcal mol-1), the regio- and stereoselective
synthesis of oxetanes is still challenging subject. In recent decades,
Scheme 1 The hydroxy-directed diastereoselectivity in the PB reaction of
however, several examples of the selective formation of oxetanes
allylic alcohols with benzophenone.
have been reported.5 Among them, the hydroxy-directed regio-
and diastereoselectivity in the PB reaction of allylic alcohols
has attracted considerable attention from both the synthetic and
mechanistic point of view.6 The origin of the hydroxy-directed
formation of oxetanes OX was recently concluded to be hydrogen-
bonding stabilization not in the biradical intermediate BR, but in
the exciplex intermediate EX (Scheme 1).7
In the present study, geraniol (1a) and its derivatives 1b,c were
chosen to see how the hydroxyl group affect the regioselectivity
in the formation of oxetane (Scheme 2). They contain the allylic
alcohol functionality as well as the unfunctionalized double bond.
a1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-8526, Japan.
E-mail: mabe@hiroshima-u.ac.jp; Fax: +81-82-424-7432; Tel: +81-424-
7432
bJapan Science and Technology Agency, CREST, 5 Sanbancho, Chiyodaku,
Tokyo, 102-0075, Japan
† This article is published as part of a themed issue in honour of Yoshihisa
Inoue’s research accomplishments on the occasion of his 60th birthday.
‡ Electronic supplementary information (ESI) available: 1H and 13C-NMR
spectra of compounds 2a–c and 3a–c. See DOI: 10.1039/c1pp05056g
Scheme 2 The PB reaction of geraniol derivatives 1 with benzophenone.
This journal is The Royal Society of Chemistry and Owner Societies 2011 Photochem. Photobiol. Sci., 2011, 10, 1469–1473 | 1469
©

Table 1 The PB reaction of 1a with benzophenonea
Entry
Solventb
Conc. (mM)
Temp. (◦C)
2a (%)c
3a (%)c
2a/3a
4, 5, 6 (%)
1
2
tol.
tol.
tol.
ben.
tol.
tol.
tol.
ben.
340
340
340
340
6.8
6.8
6.8
6.8
-75
-40
20
13d
14d
16e
15e
27d
18d
10f
20f
44
38
26
29
28
20
12
26
23/77
27/73
38/62
35/65
49/51
47/53
46/54
44/56
12, 1, 1
14, 1, 1
22, 2, 1
18, 0, 0
13, 9, 2
26, 14, 5
43, 29, 16
14, 0, 0
3
4g
5
20
-75
-40
20
6
7
8h
20
1
a Irradiation was carried our under nitrogen atmosphere. b tol. = toluene; ben. = benzene. c Yields were determined by H NMR analysis (500 MHz),
Ph3CH as an internal standard; error 3%. Ph3CH was added after the photolysis. d trans/cis = >97/3. e trans/cis = 76/24. f trans/cis = 77/23. g The
quantum yield (U) of compounds 2a and 3a was determined to be 0.32. h The quantum yield (U) of compounds 2a and 3a was determined to be 0.15.
give nearly the 1 : 1 mixture of oxetanes 2a and 3a, and also the
increase of the formation of compounds 4–6 was observed (entries
Results and discussion
First of all, the regioselectivity of the PB reaction of 1a (R =
H) with benzophenone was investigated using a high-pressure
Hg lamp (150 W) through a Pyrex filter (hn > 290 nm) in a
dried and oxygen-free toluene or benzene solution (Scheme 2,
Table 1). Toluene is a useful solvent to see the effect in a wide
range of temperatures. In accordance with the hydroxy-group
directivity, the oxetane formation at the 2,3 double bond should
be preferred over the 6,7 one to afford oxetane 2a selectively.
As shown in entries 1–4, however, the regioselective formation
of oxetane 3a derived from the reaction at the 6,7 double bond
was observed at the concentration of [1a] = 340 mM; 2a/3a = ca.
30/70. Compounds 4–68 were also isolated in the photochemical
reaction. The structure of compounds 2a and 3a was determined
by measuring the 2D-NMR spectra. Thus, the methine (CH)
proton of the oxetane ring in 2a was found to be coupled
with the methylene protons (–CH2OH) of 2a. Alternatively, the
methylene protons (CH2OH) in 3a was found to be coupled with
the vinyl proton of 3a. The formation of 2a slightly increased
with increasing the reaction temperature, e.g. 2a/3a = 23/77 at
-75 ◦C and 2a/3a = 38/62 at 20 ◦C (entries 1–4). At the lower
concentration [1a] = 6.8 mM, the formation of 2a increased to
5–8). Thus, the regioselectivity (2a/3a) was found to be dependent
on the concentration of the alcohol. The concentration effect on
the selectivity suggests that the intermolecular association of 1a
plays a role in determining the regioselectivity (Scheme 3). In
1
fact, the H NMR resonance of the hydroxyl proton (OH) of 1a
was temperature and concentration sensitive (Fig. 1a,b). Thus,
a downfield shift of the proton resonance was observed from
d 1.82 (20 ◦C) to 5.62 (-60 ◦C) with a decrease in temperature
when geraniol 1a (340 mM) and benzophenone (170 mM) were
dissolved in dried toluene-d8 (Fig. 1a). No change was observed in
the resonance of the ortho-protons of benzophenone (d 7.88). A
similar shift in the hydroxyl proton resonance was also observed in
the absence of benzophenone, i.e. d 1.68 (20 ◦C) to 5.64 (-60 ◦C).
As shown in Fig. 1a, however, significant downfield shifts were
observed for the vinylic proton Hb and the allylic protons Hc, Hb;
d 5.41 (20 ◦C) to 5.65 (-60 ◦C), Hc; d 4.02 (20 ◦C) to 4.29 (-60 ◦C).
The shift in the resonance for Ha was quite small, d 5.14 (20 ◦C)
to 5.19 (-60 ◦C). At lower concentration of 1a (Fig. 1b), a small
shift in the resonance of the OH proton was observed, d 0.45
(20 ◦C) to 0.63 (-60 ◦C). Thus, the hydrogen-bonded association
of 1a was revealed at lower temperature and higher concentration
Scheme 3 Mechanism of the PB reaction of 1 with benzophenone.
1470 | Photochem. Photobiol. Sci., 2011, 10, 1469–1473 This journal is The Royal Society of Chemistry and Owner Societies 2011
©

trans-cis isomerization in the 2,3-double bond moiety, which was
observed in the formation of oxetane 2a at 20 ◦C (entries 3, 4, 7, 8
in Table 1), was rationalized by the conformational change in the
triplet biradicals during the intersystem crossing (ISC) process
to the singlet state. The formation of 4–6 is explained by the
reaction initiated from the hydrogen-abstraction of the triplet state
of benzophenone (Scheme 4).
Scheme 4 Mechanism for the formation of 4–6.
Conclusions
In this study, we have examined the hydroxy-group directivity
in the PB reaction of geraniol derivatives. In the reaction of
1a, oxetanes 2a and 3a was obtained in a ratio of nearly the
1 : 1 mixture. The PB reaction of the hydroxy-protected 1b,c
produced regioselectively oxetanes 3b,c, which are derived from
the reaction at the unfunctionalized double bond. The inductive
electron withdrawal by the hydroxy/alkoxy group will lower the
nucleophilicity of the 2,3 double bond, if this electronic property is
the decisive reactivity factor, the preferential oxetane-formation at
the 6,7 double bond would be expected. Actually, the selective
formation of 3b,c was observed in the PB reaction of 1b,c.
However, the significant increase of the formation of 2a was found
in the reaction of 1a. The experimental results clearly indicate that
the hydroxy directivity plays an important role in increasing the
formation of 2a.
Fig. 1 Valuable temperature 1H NMR spectra of 1a (500 MHz, C7D8) at
(a) higher concentration of [1a] = 340 mM and [Ph2CO] = 170 mM, and
(b) lower concentration of [1a] = 6.8 mM and [Ph2CO] = 3.4 mM.
of 1a (Scheme 3). At higher concentration of alcohol 1a (R = H)
and low temperature, the hydrogen-bonding stabilization in the
exciplex EX2a would be suppressed, since the association of 1a
such as dimerization masks the hydroxyl group (Scheme 3).
To obtain more information about the hydroxyl group effect
on the regioselectivity, the PB reactions of the hydroxy-protected
methyl ether 1b9 and acetate 1c10 with benzophenone were
investigated in a dried and oxygen-free toluene solution (Table
2). As shown in entries 1–4, the regioselectivity, 2/3 = 15/85–
11/89, was not dependent on the concentration of 1b,c. Thus, the
electrophilic oxygen of the benzophenone triplet state preferably
approaches to the more nucleophilic 6,7 double-bond to afford
the triplet biradical BR3 via the exciplex EX3 (Scheme 3). The
Experimental
General procedure for the photoreactions of benzophenone with
geraniol derivatives
A dried and degassed toluene solution of freshly prepared geraniol
derivatives 1a–c and benzophenone was irradiated for 6 h with a
high-pressure Hg lamp through a Pyrex filter at various temper-
atures and concentrations. After the solvent was removed under
reduced pressure using a vacuum pump (0.2 mmHg, < 10 ◦C),
1
the photolysate was directly analyzed by H NMR (500 MHz)
spectroscopy. The product yields were determined on the basis of
the 1H NMR (500 MHz) peak areas; error 3%. Triphenylmethane
(Ph3CH) was added after the photolysis, and used as an internal
standard. The product ratios were determined by comparisons of
the peak areas. The photoproducts were isolated using silica-gel
column chromatography.
Table 2 The PB reaction of 1b,c with benzophenonea
Entry 1 Conc. (mM) Temp. (◦C) 2 (%)b 3 (%)b 2/3
4, 5, 6 (%)
1
2
3
4
1b 340
1b 6.8
1c 340
1c 6.8
-75
-75
-75
-75
2b (6)c 3b (33) 15/85 9, 1, 1
((2S,3R)-3-Methyl-3-(4-methylpent-3-en-1-yl)-4,4-diphenyloxe-
tan-2-yl)methanol (2a). 1H NMR (500 MHz, C6D6): d 1.02 (s,
3H), 1.40–1.50 (m, 2H), 1.45 (s, 3H), 1.54 (s, 3H), 1.69–1.78 (m,
1H), 1.82–1.93 (m, 1H), 3.47–3.53 (m, 1H), 3.59–3.65 (m, 1H),
4.52 (dd, J = 5.56 and 6.19 Hz, 1H), 4.90–4.95 (m, 1H), 6.97–
7.05 (m, 2H), 7.13–7.20 (m, 4H), 7.46–7.50 (m, 2H), 7.67–7.71 (m,
2H); 13C NMR (125 MHz, C6D6): d 17.57 (CH3), 17.95 (CH3),
2b (5)c 3b (29) 15/85 17, 12, 3
2c (7)c 3c (56) 11/89 4, 2, 2
2c (5)c 3c (39) 11/89 18, 16, 3
a Irradiation was carried our under nitrogen atmosphere. b Yields were
determined by 1H NMR analysis (500 MHz), Ph3CH as an internal
standard; error 3%. c trans/cis = > 97/3.
This journal is
The Royal Society of Chemistry and Owner Societies 2011 Photochem. Photobiol. Sci., 2011, 10, 1469–1473 | 1471
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23.73 (CH2), 25.63 (CH3), 39.54 (CH2), 48.56 (C), 63.25 (CH2),
84.37 (CH), 92.09 (C), 124.82 (CH), 125.56 (CH), 126.18 (CH),
126.60 (CH), 126.85 (CH), 128.05 (CH), 128.29 (CH), 131.24 (C),
144.20 (C), 145.47 (C); EI-MS (M+): Calcd for C23H28O2, 336.2089;
Found, 336.2097; IR (neat, cm-1): 3434, 3058, 2968, 2929, 2870,
1737, 1448, 990, 709.
7.56–7.61 (m, 2H); 13C NMR (125 MHz, CDCl3): d 16.50 (CH3),
21.19 (CH3), 26.12 (CH3), 29.95 (CH2), 34.91 (CH2), 45.51 (C),
57.84 (CH3), 68.94 (CH2), 85.11 (CH), 90.44 (C), 120.98 (CH),
125.06 (CH), 125.61 (CH), 126.22 (CH), 126.36 (CH), 127.62
(CH), 127.90 (CH), 139.82 (C), 144.34 (C), 145.22 (C); ESI-MS
([M+Na]+): Calcd for C24H30O2Na, 373.2138; Found, 373.2144;
IR (neat, cm-1): 3058, 2957, 2932, 2871, 1673, 1448, 1103, 996,
709.
(E)-5-(3,3-Dimethyl-4,4-diphenyloxetan-2-yl)-3-methylpent-2-
en-1-ol (3a). 1H NMR (500 MHz, C6D6): d 0.95 (s, 3H), 0,99 (s,
3H), 1.43–1.53 (m, 1H), 1.49 (s, 3H), 1.73–1.85 (m, 1H), 1.88–1.98
(m, 1H), 2.15–2.25 (m, 1H), 3.99–4.05 (m, 2H), 4.29 (dd, J = 4.29
and 8.76 Hz, 1H), 5.42–5.49 (m, 1H), 6.98–7.08 (m, 2H), 7.12–
7.25 (m, 4H), 7.53–7.58 (m, 2H), 7.68–7.73 (m, 2H); 13C NMR
(125 MHz, C6D6): d 16.18 (CH3), 21.28 (CH3), 26.08 (CH3), 30.28
(CH2), 35.21 (CH2), 45.59 (C), 59.29 (CH2), 85.23 (CH), 90.73
(C), 125.06 (CH), 125.49 (CH), 126.06 (CH), 126.53 (CH), 126.70
(CH), 127.95 (CH), 128.26 (CH), 137.74 (C), 144.97 (C), 145.88
(C); EI-MS (M+): Calcd for C23H28O2, 336.2089; Found, 336.2084;
IR (neat, cm-1): 3400, 3057, 2959, 2934, 2870, 1669, 1447, 996, 709.
(E)-3,7-Dimethylocta-2,6-dien-1-yl acetate (1c). In a flame-
dried 50 mL two-neck round bottom flask, equipped with
magnetic stir bar, were placed geraniol 1a (3.0 mL, 17.29 mmol),
triethylamine (2.7 mL, 19 mmol) and dry CH2Cl2 (15 mL)
via syringe. The flask was cooled in an ice bath and acetic
anhydride (1.8 mL, 19 mmol) was added dropwise via syringe.
The resulting solution was stirred under a stream of nitrogen at
room temperature overnight. The reaction mixture was washed
with H2O (20 mL), NaHCO3 (2 ¥ 20 mL) and H2O (20 mL) and the
aqueous extracts were back-extracted with CH2Cl2 (20 mL). The
combined organic layer was washed with brine, dried over Na2SO4,
and concentrated. The residue was purified by flash column
chromatography (hexane–EtOAc = 9 : 1 v/v) to give colorless oil
(2.96 g, 15.07 mmol, yield = 87%). 1H NMR (CDCl3, 500 MHz):
d1.60 (s, 3H), 1.68 (s, 3H), 1.70 (s, 3H), 2.01–2.14 (m, 7H), 4.58 (d,
J = 7.08 Hz, 2H), 5.05–5.10 (m, 1H), 5.31–5.36 (m, 1H); APCI-MS
([M+H]+): Calcd for C12H21O2, 197.1536; Found, 197.1533.
(E)-1-Methoxy-3,7-dimethylocta-2,6-diene (1b). NaH (0.35 g,
8.65 mmol) was washed with hexane. The washed NaH was
dissolved in dry THF (10 ml). To this solution, geraniol 1a (1.00 g,
6.50 mmol) in dry THF (10 ml) was added dropwise. The reaction
◦
mixture was stirred 1 h at 0 C. After the addition, MeI (1.41 g,
9.90 mmol) in dry THF (10 ml) was added to the reaction mixture
at rt. After the addition, the reaction mixture was stirred over
night. The reaction mixture was quenched by the addition of water
and extracted with ether. The combined organic layer was washed
with brine, dried over MgSO4, and concentrated. The residue was
purified by flash column chromatography (hexane–EtOAc = 9 : 1
v/v) to give yellow oil (0.95 g, 5.65 mmol, yield = 87%). 1H NMR
(500 MHz, CDCl3): d 1.60 (s, 3H), 1.68 (s, 6H), 2.02–2.07 (m, 2H),
2.08–2.14 (m, 2H), 3.32 (s, 3H), 3.93 (d, J = 6.78 Hz, 2H), 5.07–
5.13 (m, 1H), 5.32–5.37 (m, 1H); 13C NMR (125 MHz, CDCl3): d
16.39 (CH3), 17.63 (CH3), 25.64 (CH3), 26.38 (CH2), 39.57 (CH2),
57.70 (CH3), 68.94 (CH2), 120.72 (CH), 123.97 (CH), 131.60 (C),
140.31 (C); APCI-MS ([M+H]+): Calcd for C11H21O, 169.1587;
Found, 169.1586.
((2S,3R)-3-Methyl-3-(4-methylpent-3-en-1-yl)-4,4-diphenyloxe-
1
tan-2-yl)methyl acetate (2c). 1H NMR (500 MHz, CDCl3): H
NMR (500 MHz, CDCl3): d 1.11 (s, 3H), 1.36–1.49 (m, 2H), 1.53
(s, 3H), 1.62 (s, 3H), 1.71–1.81 (m, 1H), 1.88–1.98 (m, 1H), 2.10 (s,
3H), 4.20–4.24 (m, 2H), 4.64 (dd, J 5.27 and 6.42 Hz, 1H), 4.88–
4.93 (m, 1H), 7.16–7.23 (m, 2H), 7.28–7.36 (m, 4H), 7.41–7.47 (m,
2H), 7.55–7.62 (m, 2H); 13C NMR (125 MHz, CDCl3): d 17.61
(CH3), 17.89 (CH3), 20.95 (CH3), 23.26 (CH2), 25.59 (CH3), 38.84
(CH2), 48.60 (C), 65.12 (CH2), 81.28 (CH), 92.32 (C), 123.86 (CH),
125.16 (CH), 125.75 (CH), 126.51 (CH), 126.70 (CH), 127.76
(CH), 128.06 (CH), 131.83 (C), 143.20 (C), 144.35 (C), 170.85
(C); ESI-MS ([M+Na]+): Calcd for C25H30O3Na, 401.2087; Found,
401.2089; IR (neat, cm-1): 3058, 2969, 2931, 2881, 1744, 1448, 1234,
995, 709.
(3R,4S)-4-(Methoxymethyl)-3-methyl-3-(4-methylpent-3-en-1-
yl)-2,2-diphenyloxetane (2b). 1H NMR (500 MHz, CDCl3): d
1.09 (s, 3H), 1.34–1.48 (m, 2H), 1.53 (s, 3H), 1.62 (s, 3H), 1.71–
1.81 (m, 1H), 1.87–1.97 (m, 1H), 3.41 (s, 3H), 3.45–3.49 (m, 1H),
3.58–3.63 (m, 1H), 4.63 (dd, J = 4.26 and 7.39 Hz, 1H), 4.90–4.95
(m, 1H), 7.15–7.21 (m, 2H), 7.27–7.34 (m, 4H), 7.42–7.47 (m, 2H),
7.57–7.62 (m, 2H); 13C NMR (125 MHz, CDCl3): d 17.58 (CH3),
17.75 (CH3), 23.32 (CH2), 25.63 (CH3), 38.86 (CH2), 48.51 (C),
59.34 (CH3), 73.77 (CH2), 82.46 (CH), 92.06 (C), 124.12 (CH),
125.23 (CH), 125.84 (CH), 126.35 (CH), 126.54 (CH), 127.66
(CH), 127.99 (CH), 131.57 (C), 143.46 (C), 144.80 (C); ESI-MS
([M+Na]+): Calcd for C24H30O2Na, 373.2138; Found, 373.2140;
IR (neat, cm-1): 3058, 2957, 2932, 2871, 1673, 1448, 1103, 996,
709.
(E)-5-(3,3-Dimethyl-4,4-diphenyloxetan-2-yl)-3-methylpent-2-
en-1-yl acetate (3c). 1H NMR (500 MHz, CDCl3): d 1.05 (s, 3H),
1.07 (s, 3H), 1.57–1.66 (m, 1H), 1.73 (s, 3H), 1.75–1.84 (m, 1H),
2.00–2.08 (m, 1H), 2.04 (s, 3H), 2.20–2.29 (m, 1H), 4.30 (dd, J =
4.87 and 8.53 Hz, 1H), 4.59 (d, J = 7.01 Hz, 2H), 5.37–5.42 (m,
1H), 7.14–7.20 (m, 2H), 7.26–7.33 (m, 4H), 7.43–7.47 (m, 2H),
7.56–7.60 (m, 2H); 13C NMR (125 MHz, CDCl3): d 16.49 (CH3),
21.02 (CH3), 21.22 (CH3), 26.07 (CH3), 29.78 (CH2), 34.92 (CH2),
45.52 (C), 61.30 (CH2), 85.00 (CH), 90.47 (C), 1118.58 (CH),
125.05 (CH), 125.60 (CH), 126.25 (CH), 126.39 (CH), 127.62
(CH), 127.92 (CH), 141.72 (C), 144.30 (C), 145.21 (C), 171.05
(C); ESI-MS ([M+Na]+): Calcd for C25H30O3Na, 401.2087; Found,
401.2085; IR (neat, cm-1): 3058, 2956, 2870, 1738, 1448, 1233, 996,
710.
(E)-4-(5-Methoxy-3-methylpent-3-en-1-yl)-3,3-dimethyl-2,2-
diphenyloxetane (3b). 1H NMR (500 MHz, CDCl3): d 1.05 (s,
3H), 1.06 (s, 3H), 1.58–1.68 (m, 1H), 1.70 (s, 3H), 1.75–1.85 (m,
1H), 1.98–2.06 (m, 1H), 2.19–2.28 (m, 1H), 3.32 (s, 3H), 3.94 (d,
J 6.70 Hz, 2H), 4.31 (dd, J = 5.41 and 8.38 Hz, 1H), 5.37–5.41
(m, 1H), 7.13–7.20 (m, 2H), 7.25–7.34 (m, 4H), 7.43–7.48 (m, 2H),
Determination of quantum yields of oxetane formation
The quantum yields of the oxetane formations from the pho-
toreaction of benzophenone with 1a were measured by xenon
1472 | Photochem. Photobiol. Sci., 2011, 10, 1469–1473 This journal is
The Royal Society of Chemistry and Owner Societies 2011
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lamp (500 W) focused at 313 nm at room temperature. The
photochemical transformation of valerophenone to acetophenone
(U = 0.33)11 was used as a chemical actinometer.
1984, pp. 425–487; (f) A. G. Griesbeck, CRC Handbook of Organic
Photochemistry and Photobiology, ed. W. M. Horspool and P.-S. Song,
CRC Press, Boca Raton, 1994, pp. 522–535 and 536–549; (g) A. G.
Griesbeck and S. Bondock, CRC Handbook of Organic Photochemistry
and Photobiology, 2nd Edn, ed. W. M. Horspool and F. Lenci, CRC
Press, Boca Raton, 2004, chapters 59 and 60; (h) M. Abe, CRC
Handbook of Organic Photochemistry and Photobiology, 2nd Ed., ed.
W. M. Horspool and F. Lenci, CRC Press, Boca Raton, chapter 62.
5 (a) T. Bach, H. Bergmann and K. Harms, J. Am. Chem. Soc., 1999, 121,
10650–10651; (b) A. G. Kutateladze, J. Am. Chem. Soc., 2001, 123,
9279–9282; (c) M. Abe, T. Kawakami, S. Ohata, K. Nozaki and M.
Nojima, J. Am. Chem. Soc., 2004, 126, 2838–2846; (d) A. G. Griesbeck,
M. Abe and S. Bondock, Acc. Chem. Res., 2004, 37, 919–928; (e) M.
Abe, J. Chin. Chem. Soc. (Taipei), 2008, 55, 479–486; (f) M. Abe, in
Handbook of Synthetic Photochemistry, ed. A. Albini and M. Fagnoni,
Wiley-VCH, Weinheim, 2010, pp. 217–239; (g) K. Matsumura, T. Mori
and Y. Inoue, J. Org. Chem., 2010, 75, 5461–5469.
6 (a) W. Adam, K. Peters, E. M. Peters and V. R. Stegman, J. Am.
Chem. Soc., 2000, 122, 2958–2959; (b) W. Adam and V. R. Stegmann,
Synthesis, 2001, 1203–1214; (c) M. D’Auria, R. Racioppi and G.
Romaniello, Eur. J. Org. Chem., 2000, 3265–3272; (d) M. D’Auria,
L. Emanuele, G. Poggi, R. Racioppi and G. Romaniello, Tetrahedron,
2002, 58, 5045–5051; (e) M. D’Auria, L. Emanuele and R. Racioppi,
Photochem. Photobiol. Sci., 2004, 3, 927–932; (f) M. D’Auria, L.
Emanuele, R. Racioppi and A. Valente, Photochem. Photobiol. Sci.,
2008, 7, 98–103.
Acknowledgements
NMR and MS measurements were made using JEOL JMN-
LA500 and Thermo Fisher Scientific LTD Orbitrap XL spec-
trometers, respectively, at the Natural Science Center for Basic
Research and Development (N-BARD), Hiroshima University.
M. A. acknowledges financial support in the form of a Grant-
in-Aid for Scientific Research on Innovative Areas “p-Space”
(No 21108516), the Scientific Research (B) (No. 19350021), and
Tokuyama Science Foundation.
Notes and references
1 (a) D. W. Norbeck and J. B. Kramer, J. Am. Chem. Soc., 1988,
110, 7217–7218; (b) J.-M. Huang, R. Yokoyama, C.-S. Yang and Y.
Fukuyama, Tetrahedron Lett., 2000, 41, 6111–6114.
2 (a) S. L. Schreiber, A. H. Hoveyda and H.-J. Wu, J. Am. Chem. Soc.,
1983, 105, 660–661; (b) J. A. Porca and S. L. Schreiber, Comprehensive
Organic Synthesis, ed. B. M. Trost, Pergamon Press, New York, 1991,
Vol. 5, p. 168; (c) A. G. Griesbeck, Organic Photochemistry and
Photobiology, ed. W. M. Horspool and P. S. Song, CRC Press, New
York, 1995, pp. 522 and 550; (d) T. Bach, Liebigs Ann./Recl., 1997,
1627–1634; (e) T. Bach, Synthesis, 1998, 683–703.
7 Y. Yabuno, Y. Hiraga, R. Takagi and M. Abe, J. Am. Chem. Soc., 2011,
133, 2592–2603.
8 (a) M. Abe, M. Terazawa, K. Nozaki, A. Masuyamaa and T. Hayashia,
Tetrahedron Lett., 2006, 47, 2527–2530; (b) M. Hatano, S. Suzuki and
K. Ishihara, J. Am. Chem. Soc., 2006, 128, 9998–9999; (c) Y. Yuan and
Y. B i a n , Appl. Organomet. Chem., 2008, 22, 15–18.
3 H. Sasaki, Prog. Org. Coat., 2007, 58, 227–230.
9 T. D. R. Manning and P. J. Kropp, J. Am. Chem. Soc., 1981, 103,
889–897.
4 (a) E. Paterno` and G. Chieffi, Gazz. Chim. Ital., 1909, 39(I), 341–361;
(b) G. Bu¨chi, C. G. Inman and E. S. Lipinsky, J. Am. Chem. Soc.,
1954, 76, 4327–4331; (c) N. C. Yang, M. Nussim, M. J. Jorgenson
and S. Murov, Tetrahedron Lett., 1964, 5, 3657–3664; (d) D. R.
Arnold, Adv. Photochem., 1968, 6, 301–349; (e) H. A. Carless, Synthetic
Organic Photochemistry, ed. W. M. Horspool, Plenum Press, New York,
10 I. D. G. Watson, S. A. Styler and A. K. Yudin, J. Am. Chem. Soc., 2004,
126, 5086–5087.
11 (a) P. J. Wagner and A. E. Kemppainen, J. Am. Chem. Soc., 1968, 90,
5896–5897.
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